Fix recognition of variable functions

[sirbrillig]

Fixes #26

[sirbrillig]

Ok, I think I found it. It's this line from the PHP docs:

When calling static methods, the function call is stronger than the static property operator:

To be more specific,

• Thing::$prop looks for a static variable named $prop on the class Thing.
• Thing::$$propName looks for a static variable called whatever the value of $propName is on the class Thing.
• $className::$prop looks for a static variable named $prop on the class called whatever the value of $className is set to.
• Thing::func() looks for a static function called func on the class Thing.
• Thing::$funcName() looks for a static function named whatever the value of $funcName is on the class Thing.

That last one is the odd one out, and the sniffs don't take it into account.